Electron discharge device and circuits



June 22, 1954 R. ADLER I ELECTRON DISCHARGE DEVICE AND CIRCUITS 2Sheets-Sheet 1 Filed Nov. 26, 1949 TIME b HIS ATTORNEY June 22, 1954ADLER I 2,681,995

ELECTRON DISCHARGE DEVICE AND CIRCUITS Filed Nov. 26, 1949 2Sheets-Sheet 2 Source lnpuf- Signal Source ROBERT ADLER INVENTOR.

aviw 0 HIS ATTORNEY Patented June 22, 1954 ELECTRON DISCHARGE DEVICE ANDCIRCUITS Robert Adler, Chicago, HL,

Radio Corporation,

assignor to Zenith a corporation of Illinois Application November 26,1949, Serial No. 129,554

25 Claims. 1

This invention relates to electron-discharge devices and to circuitsemploying such devices. It is a primary object of the present inventionto provide a novel type of electron-discharge device as a new tool inthe art, and to provide novel circuits embodying the novel device.

Most electron-discharge devices of the type utilized in electronicapplications, such as carrier-wave translating systems and the like, aresubject to the limitation of being unilaterally conductive.Consequently, the versatility of conventional devices of this type islimited to circuit applications in which current need be passed only ina single direction.

It is therefore a primary object of the present invention to provide abidirectional electron-dis charge device.

Another object of the invention is to provide a high-vacuumelectron-discharge device having an electron-discharge path which iscapable of passing current in either direction.

Yet another object of the invention is to provide a bidirectionalelectron-discharge device in which the space current flow is subject toexternal control.

Still another object of the invention is to provide an improvedelectron-discharge device capable of passing current of either positiveor negative polarity through an associated load circuit.

The unilateral character of prior art electrondischarge devices isencountered as a limitation in many circuit applications and results inmany cases in the use of complex circuits involving a large number ofcomponents to perform a desired function. One such application whichmakes this limitation readily apparent is the generation of an outputcurrent of sawtooth waveform, as for example in the production of asawtooth deflection current for use in the scanning system of atelevision receiver. Prior art arrangements for accomplishing thispurpose incorporate unilateral electrcn-discharge devices and,consequently, utilize a relatively large number of circuit components.In addition, sufficient sawtooth current for operating theline-frequency scanning system of a television receiver is only obtainedby using relatively high supply voltages.

Consequently, it is an important object of the present invention toprovide novel signalgenerating apparatus embodying a bidirectionalelectron-discharge device.

It is a further object of the invention to prospace electrons, so that 2vide improved apparatus for generating an output current of sawtoothwaveform.

Yet another object of the invention is to provide improved andsimplified apparatus for gencrating a sawtooth output current ofsufficient magnitude, for example, to drive the scanning system of atelevision receiver while reducing the supply voltage requirements.

In accordance with one feature of the present invention, a new andimproved bidirectional high vacuum electron-discharge device having abidirectional electron-discharge path comprises a pair of thermioniccathodes and a control electrode disposed between the cathodes forcontrolling electron space current flow therebetween. Furthermore, oneof the cathodes is preferably arranged to be heated by radiation fromthe other cathode.

In accordance with still another feature of the invention,signal-generating apparatus for generating an output current of sawtoothwaveform comprises a bidirectional electron-discharge device having apair of thermionic cathodes and a control grid intermediate the cathodesfor controlling electron space current flow therebetween. An inputcircuit is coupled between the control grid and one of the cathodes, andan input-signal source is coupled to the input circuit for applying tothe control grid control pulses of predetermined time duration shortrelative to their periodicity. An output load circuit, resonating at afrequency having a period at least equal to substantially twice thepredetermined time duration of the individual control pulses, is coupledbetween the cathodes, and means are provided for impressing aunidirectional operating potential difference between the cathodes andin series with the output load circuit.

Throughout the specification and the appended claims, the term cathodeis used as definitive of an electrode which is capable of thermionicemission and is not intended to be restricted to an electrode which isconnected to the negative terminal of the external circuit. Furthermore,the term bidirectional, as applied to an electron-discharge device or toan electron-discharge path, is to be interpreted to mean that the deviceor the path is capable of passing current in either direction, ascontrasted with prior art devices which are unilaterally conductiveonly. A bidirectional electron-discharge path is thus construed as onewhich is defined by terminating electrodes each of which is capable ofsupplying space current flow may 33 be established in either directionby providing appropriate operating potentials.

lhe features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The invention,together with further objects and advantages thereof, may best beunderstood, however, by reference to the following description takenconnection with the accompanying drawings, in the several figures ofwhich like reference numerals indicate like elements, and in which:

Figure 1 is a cross-sectional view of an electron-discharge deviceconstructed in accordance with the present invention;

Figure 2 is a cross-sectional view embodiment of the invention;

Figure 3 is a schematic circuit diagram signal generator embodying theinvention;

Figure 4 is an idealized graphical represei'rtation useful inunderstanding the operation of the circuit of Figure 3, and

Figures 5, 6 and 7 are schematic diagrams of further embodiments of theinvention.

In Figu e i, an electron-discharge device constructed in accordance withthe invention comprises, within an evacuated envelope it], a pair ofthermionic cathodes and a control grid intermediate the cathodes.Preierabl the first cathode comprises a pair oi members ii and it havingthermionically emissive surfaces 53 and it respectively. The secondcathode is is dispo e between members H and i2 and is provided with apair of thermionically emissive surfaces and ii opposite surfaces i3 andi i respectively. Suitable means are provided for heating members i iand !2 of the first cathode and second cathode l; for example,individual heater elements may be provided for each cathode member. Acontrol grid- E8, which may be of the parallehwire type, is arranged tosurround second cathode i5, and the conductive grid elements aredisposed between second cathode l5 and members it and 92. Con-- trolgrid 58 may be conveniently supported by means of side-rods is andMembers ii and it are connected together for operation at a commonpotential by circuit means (not shown) which may be either internal orexternal oi evacuated envelope A device constructed as shown in Figure lis highly unconventional in that it is capable of passing electron spacecurrent in either direction between the first cathode, comprisingmembers i l and E2, and the second cathode 55, depending on the relativeoperating potentials applied to the two cathodes. Thus, at a particularinstant of time, second cathode iii may be maintained at a potentialhigher than that of first cathode members ii and i2. In this event,second cathode i5 instantaneously operates as an anode or collector forelectrons originating at emissive surfaces !3 and i i. Electronsemanating from emis sive surfaces l5 and ii encounter a retarding field,due to the lower operating potential of first cathode members i! and i2,and are prevented from reaching the first cathode.

Conversely, if at another instant of time first cathode members ii andiii are operated at a potential higher than that of second cathode iii,the first cathode members operate instantaneously as an anode orcollector for electrons originating at emissive surfaces l5 and I7, andelectrons emanating from surfaces l3 and Hi are suppressed.

Control grid l8 serves as a convenient means for controlling theelectron space current flow of another ofa between the cathodesconstituting the terminating electrodes for the electron-discharge path.At any instant of time, the control grid has an effective amplificationfactor or mu relative to the terminating electrode acting as anode atthat instant, since the device operates instantaneously as aconventional triode. However, the device differs from conventionalelectron-discharge amplifiers in the bidirectional nature of thedischarge path.

It is important to note that the control grid iii is preferably operatedat a positive potential with respect to the cathode instantaneouslyoperating as the electron space current source for the unconventionalpurpose of controlling the emission-current density of that cathode.While such operation results in a large amount of grid current, thevoltages involved are small so that the power dissipated in the gridcircuit is not excessive.

For convenience, it is possible to operate the device of Figure l withfirst cathode members ll and i2 maintained at a fixed referencepotential such as ground. The direction of electron space current flowis then dependent upon whether the instantaneous potential of secondcathode i5 is above or below the fixed reference potential applied tomembers H and I2. For conduction in either direction, it is apparentthat there must be a potential difference between the two cathodes.Furthermore, large voltage pulses may be produced if the control grid isdriven sharply beyond cut-off and if an inductive load impedance isconnected in the output circuit. Consequently, it is necessary with thedevice of Figure l to take the precaution of properly insulating theheater elements associated with the respective cathodes. Such insulationmay conveniently be accomplished in the filament transformer; however,such special insulation of the filament transformer windings is costly.

An electron-discharge device constructed in accordance with theinvention which obviates the necessity for special insulation betweenthe windings cf the filament transformer is illustransverse section inFigure 2. As before, the device comprises first cathode members it and!2 having emissive surfaces 53 and i l respectively. The second cathodei5 is disposed between members ii and i2 and provided with emissivesurfaces it and El facing members H and i2 respectively. Again, acontrol grid !8 supported by side-posts i9 and if; is arranged tosurround second cathode 5 with its conductive grid elements intermediatesecond cathode l5 and first cathode members ii and E2. Members ii and 52are indirectly heated, as in the embodiment of Figure 1, by conventionalheater elements disposed within the cathode sleeves. However, secondcathode lli is heated in another manner. For this purpose, heat-shieldmembers 2! and 22 are arranged in heat-reflecting rela ticn with firstcathode members H and 12 respectively, so that heat developed in thefirst cathode members is directed inwardly to second cathode 5 to raisethe temperature of that cathode to a sufiicient extent to establishthermionic emission. Since the envelope if! is evacuated, the onlysubstantial heat loss is by radiation so that heating by radiation,direct as well as reflected, is relatively efficient, and second cathodei5 may be raised to its emission temperature within a relatively shortperiod of time.

As explained in connection with Figurel, second cathode l5 operatesinstantaneously as a 5. collector or anode for electrons originating atsurfaces 13 and M when the potential of second cathode I is higher thanthat of first cathode members H and I2. When the second cathode i5 isoperating as an electron collector, additional heat is developed at theelectrode by its plate dissipation in the role of anode. It has beenfound that sufficient heat may be generated in second cathode l5 by thearrangement shown in Figure 2 to establish electron emission fromsurfaces l6 and l! and thereafter to maintain second cathode I 5 at orabove emission temperature, particularly when the device is used incircuits of the type hereinafter to be described, in which the secondcathode I 5 serves as anode, and therefore develops heat by platedissipation, during a substantial portion of each oper ating cycle.Therefore, the requirement for a separate heater element associated withsecond cathode I5 is obviated, and by operating first cathode members Hand I2 at ground potential, costly special insulation in the filamenttransformer need not be provided.

In order to prevent overheating of the control grid i3, radiating fin 23and 24 may be welded or otherwise secured to supporting posts it and 28respectively. Preferably, the inner surfaces of fins 23 and 24 arepolished and the outer surfaces are blackened for optimum heatdissipation.

The devices of Figures 1 and 2 may be constructed of conventional parts.For example, commercially available cathode members, having oxidecoatings, may be employed, and the grid 58 may conveniently be made byusing sideposts l3 and 26 of a diameter equal to the desired spacingbetween opposite sides of the grid. All of the electrodes may besupported between a pair of mica spacers (not shown) within envelopeill, and the device may be tered, and based in a manner well known inthe art. Cathode members ll and I2 may be connected together internallyor, alternatively, separate external connections may be provided forthese members.

While each of the devices of Figures 1 and 2 comprises a pair ofphysically separate electron paths arranged in parallel, it is withinthe scope of the invention to construct a device comprising only twocathode members defining a single electron path. The parallel-patharrangement is particularly advantageous in that it effectively doublesthe current capacity of the device, and lend itself well to manufacturein large quantities by well-known production techniques.

A bidirectional electron-discharge device of the type shown in Figures 1and 2 is a versatile new tool in the art and may be adapted to manypurposes; by way of example, it is particularly useful insignal-generating apparatus for producing an output current of sawtoothwaveform.

Signal-generating apparatus of this type is illustrated schematically inFigure 3, in which the cathodes 30 and 3| of a bidirectional electrondischarge device 32 are connected in series with a source ofunidirectional operating potential, here shown as a battery 33, and theprimary winding 3% of an output transformer 35. An input-signal source36, of negative-polarity pulses of predetermined time duration which isshort relative to their periodicity, is coupled between the control grid3'! of device 32 and first cathode 30 by means of an input transformer38 having primary and secondary windings 39 and 40 respectively; acurevacuated, getwhich may be a source rent-limiting resistor 4| isincluded in series with secondary winding 38 and control grid 37. Firstcathode 30 is directly connected to ground.

In the circuit of Figure 3, device 32 is main tained in a conductivestate except for a short interval during each cycle. During the firstportion of the conductive period, inductor 34 delivers power to battery33; during the second half of the conductive cycle, power is deliveredfrom battery 33 to load inductor 34. If there were no losses in thecircuit, the net direct-current component would be zero, due to thebidirectional character of the current in the series circuit comprisingdevice 32, inductor 34, and battery 33.

At the end of the desired conductive period, a negative pulse issupplied to control grid 3? to cut oil device 32, thus interruptingcurrent flow in the series output current path. Consequently, inductor34, together with its parallel capacity 42, goes through substantiallyone-half cycle of free oscillation. Capacity 42 may conveniently consistof capacity reflected from sec ondary winding 43. of output transformer35 and from circuits connected thereto (not shown), and is of suflicientmagnitude to resonate with inductor 34 at a frequency having ahalf-period substantially equal to the predetermined time duration ofthe individual control pulses. Consequently, when the control pulse isremoved from control grid 31 and device 32 again becomes conductive, thecurrent through coil 36!- has shifted in phase by substantially and theoutput current cycle is repeated.

Since the time rate of change of current from a constant unidirectionalVoltage source through a constant inductor is constant and dependentonly on the ratio of the Voltage of the source to the inductance of theload, the output current during the conductive period is of constantslope, and this slope may be adjusted to any desired value by suitableselection of operating potential and load inductance. The flyback timefrom the end of one conductive period to the beginning of the next maybe very short and is determined by the natural half-period of outputinductor 34 and capacity 32. Since capacity 42 is very small,particularly when it constitutes only the capacity reflected fromsecondary winding 43 and the circuits connected thereto, the flybacktime may pid. Hence it is apparent that the ClI'Clllb of Figure 3 may beused to advantage to yokes of a television receiver with deflectioncurrent of sawtooth waveform for scanning purposes.

For a better understanding of the operation of the circuit of Figure 3,reference is now made to the waveforms of Figure 4, in which curves ofinput voltage, control grid voltage (or control signal) second-cathodevoltage, and second-cathode current are plotted as functions of time.The input voltage 6i, appearing across secondary winding 4c of inputtransformer 38 from input-- signal source 36, may conveniently consistof a series of periodic negative-polarity control pulses individuallyhaving a predetermined time duration. Since the input voltage isimpressed across a coil $0, the average input voltage over each cyclemust be zero. Consequently, the input voltage e1 is slightly positiveduring the intervals between successive control-signal pulses 50 and El.Dur ing these intervals, therefore, grid current tends to be drawn.However, series resistor 41 included in the input circuit serves tolimit this grid current so that the control signal 6g applied betweencontrol grid 3! and first cathode 30 comprises negative pulses 52 and 53between which the grid voltage gradually rises from a value which isinitially slightly negative at the beginning of the conductive period toone which is positive at the end of the conductive period. The voltageer of the second cathode 3! with respect to ground is somewhat morenegative than that of the control grid 31 at the beginning of theconductive period and somewhat more positive at the end of theconductive period.

When the control pulses 52 and 53 are applied to grid 31, electron spacecurrent flow in device 32 is cut off and the series output circuit isopened. The voltage er then oscillates at a irequency determined byinductor 34 and capacity until the control pulse is removed from controlgrid 3i. By making capacity 42 of such magnitude that it resonates withinductor 34 at a frequency having a half-period substantially equal tothe predetermined time duration of each of the control pulses, thevoltage e1; is caused to oscillate through substantially one-half cycleduring the cut-off period, so that the voltage ck swings up to apositive peak and then rapidly downward to a negative value at thebeginning of the next conductive period, thus insuring proper phasing ofthe output curren The output current which also represents the currentthrough device 32, is of substantially a sawtooth wave form, andreverses in direction or polarity near the middle of the conductiveperiod. The output current ik is, of course, zero during the intervalsof control pulses 52 and 53, since device 32 is non-conductive duringthese intervals.

Ideally, the current should reverse direction exactly at the middle ofthe conductive period, so that the peak positive and negative currentsare equa; in such a case, no direct-current component would appear inthe output. In practice, however, the load is not purely inductive andsome voltage drop is required between the oathodes to obtain therequired flow of current. There is, therefore, an energy loss duringeach cycle, and the negative current after flyback is of smallermagnitude than the positive current at the end of the conductive period.Consequently there is a small net direct-current component in theoutput.

In order to avoid undesirable space charge effects which might result infurther energy loss and in non-linearity in the output current waveform,it is desirable to select the values of the severalcircuit components sothat the voltage 5g of control grid 31 with respect to ground changessign somewhat before the voltage er of the second cathode 3i withrespect to ground swings from negative to positive. This operation hasbeen illustrated in the graphical representation of Figure l, in whichthe grid voltage c swings through zero at a time 151 slightly before thetime when the voltage ck changes sign.

It is noted that the waveforms of Figure 4 are drawn to differentscales, the pulses appearing at the second cathode during flyback beingmany times larger in peak value than the negative control pulses appliedto grid 3 In practice, the system of Figure 3 is not only very simple,but is also much more efficient than conventional sawtooth currentgenerators. The voltage drop across device 32 may be as low as tenvolts, so that a supply voltage of about 100 volts sufficies to obtaineilicient operation. The current density within the tube is dependentupon the potential difference between the grid and'the instantaneousspace-electron source; if the spacmg is about .010 inch, ten volts ofpositive grid potential sumce to provide a current density of about 120milliamperes per square centimeter, which is about the maximumrecommended for oxide-coated cathodes from a cathode-life standpoint.

To operate the line-frequency scanning system of a television receiverusing a 12-inch pic ture tube with a supply voltage of about voltsrequires a peak-to-peak sawtooth output current of the order of 500milliamperes, or plus-andminus 250 milliamperes neglecting thedirect-current component. Consequently, sufficient space current may besupplied for this application by cathodes having emitting areas of a fewsquare centimeters. Of course, larger output currents may be obtained byusing larger cathode emitting areas.

With the arrangement of Figure 3, substantial amounts of grid currentare drawn. The circuit of Figure 5 is a modification in which the amountof grid current is reduced and, therefore, the effieiency of the circuitis increased. The circuit is identical with that of Figure 3 with theexception that a self-biasing condenser 60 is connected in the inputcircuit in parallel with current-limiting resistor 4|. Thus, the controlgrid 31 is selfbiased. With this arrangement, a sawtooth driving voltageis superimposed on the pulse-signal to provide an input-signal having awaveform similar to that of the control grid voltage e of Figure 4. Itis possible so to adjust the value of resistor ii that less grid currentis drawn and higher efiiciency is obtained than with the circuit ofFigure 3.

When the slope of the sawtooth component of the input-signal is lessthan the desired value, it may be advantageous to insert an unbypassedseries resistor (not shown) in series in the input circuit between coilis and control grid 31.

In accordance with another feature of the invention, it is possible toderive the control pulses for cutting off device 32 from the outputcircuit. Such an arrangement is illustrated in Figure 6, in which afeedback coil 65, inductively coupled to output inductor 34, isseries-coupled in the input circuit. Preferably, the voltage ratio ofthe feedback coil 65 with respect to the output inductor 3c is madesubstantially equal to the reciprocal of the effective amplificationfactor of control. grid 31 with respect to second cathode 3 i, so thatthe voltage pulse fed back to the input circuit is of sufficientmagnitude to render device 32 con-conductive. With such an arrangement,the input-signal from source 35 comprises only pulses of relativelysmall amplitude to insure that cut-off be initiated at the proper time.Alternatively, the input-signal may comprise a single sawtooth wave ofsufficient amplitude to initiate cut-off at the beginning of the flybackperiod. To obtain greater grid current efficiency, a self-biasingcondenser may be connected in parallel with resistor ll and theinputsignal from source 38 may be of the same type as signal 5| appliedto the circuit of Figure 5, comprising a sawtooth wave superposed onperiodic negative-polarity pulses; however, the input pulses need beonly of relatively small ma nitude.

When the control pulses are derived from the output circuit, as by meansof feedback coil 65, the input pulses from source 36 need be only ofrelatively Small magnitude. When the voltage ratio of feedback coil 65with respect to inductor between the grid and each of the cathodes- 34is made equal to the reciprocal of the effective amplification factor ofdevice 32 measured from grid 3"! to second cathode 3|, the input pulsesshould be of a time duration substantially equal to the naturalhalf-period of inductor 34 and capacity Input pulses of shorter timeduration may be used it the volta e ratio of feedback coil (55 withrespect to inductor 34 exceeds the reciprocal of the effectiveamplification factor, so that, in a generic sense, it is necessary thatcapacity 42 be of magnitude to resonate with inductor i l at a frequencyhavin a period at least equal to substantially twice the time durationof an individual input pulse.

The circuit of Figure '7 illustrates still another embodiment of theinvention in which the sawtooth component of the control signal isderived from the output circuit. To this end, a small load resistor 15]is connected in series between first cathode til and ground. The primarywinding ii of a voltage transformer 12 is connected in parallel withresistor iii, and the secondary windin is of transformer i2 isseries-coupled in the input circuit between secondary winding ltl ofinput transformer 38 and feedback coil 65. The voltage fed back to theinput circuit by way of transformer '12 comprises a control potential ofsawtooth waveform which, when superposed on the voltage pulses fed backby way of feedback coil 65, operates to control the grid potential inthe desired manner during the conductive period. Since the controlsignal comprises a sawtooth component, a self-biasing condenser as isused as in Figure 5. Again, the voltage ratio of feedback coil 65 withrespect to output inductor (it is preferably made substantially equal tothe reciprocal of the effective amplification factor of device 32 asmeasured from control grid 37 to second cathode 3|. With thisarrangement, still greater grid current eificiency may be obtained withan input-signal from source 36 comprising negative pulses of relativelysmall magnitude.

Thus, the present invention provides, as a new tool in the art, anelectron-discharge device having a biderectional electron-dischargepath. Furthermore, the invention provides novel signalgeneratingapparatus embodying such a tube, and particularly, novel apparatus forgenerating an output current of sawtooth waveform with a minimum numberof components at an efiiciency much greater than that provided by priorart arrangements using conventional unilateral electron-dischargedevices.

While particular embodiments of the present invention have been shownand described, it is apparent that various changes and modifications maybe made, and it is therefore contemplated in the appended claims tocover all such changes and modifications as fall within the true spiritand scope of the invention.

I claim:

1. A bidirectional electron-discharge device comprising: a first cathodeincluding a pair of cathode members each having an emissive sur face; asecond cathode disposed between said members and having a pair ofemissive surfaces; and a control grid including conductive grid elementsintermediate said second cathode and said members for controllingelectron space current flow between said cathodes.

2. A bidirectional electron-discharge device comprising: a firstthermionic cathode having an emissive surface; a heater for energizingsaid first cathode; a second thermionic cathode hav to one of saidcathodes for applying ing an emissive surface opposed to that of saidfirst cathode and arranged to be heated by radiation from said firstcathode; and a control grid disposed between said emissive surfaces forcontrolling electron space current iiow therebetween.

3. A bidirectional electron-discharge device comprising: a firstthermionic cathode having an emissive surface,- a heater for energizingsaid first cathode; a second thermionic cathode having an emissivesurface opposed to that of said first cathode and arranged to be heatedby radiation from said first cathode; a heatdefiecting shiclusubstantially surrounding said cathodes; a control grid disposed betweensaid emissivc surfaces for controlling electron space current flowtherebetwcen; and radiating fins secured to said control grid to preventoverheating of said grid.

4. A bidirectional high-vacuum electron-disdevice comprising: a firstthermionic cathode including a pair of cathode members each having anemissive surface; means for indirectly heating each of said members; asecond thermionic cathode disposed between said mere-- bers and having apair of emissive surfaces arranged to be heated by radiation from saidinembore; a heat-refiecting shield substantially surrounding saidcathodes; and a control grid sur rounding said second cathode and havingconductive grid elements disposed between said second cathode and saidmembers to control elec tron space current flow between said cathodes.

5. Signal-generating apparatus comprising: a source of unidirectionaloperating potential; a reactive load circuit; and an electronicswitching device including a high-vacuum thermionic electron-dischargedevice having a bidirectional clectromdischarge path coupled in serieswith said source and said circuit for controlling current flow in saidcircuit.

6. Signal-generating apparatus comprising: a source of unidirectionaloperating potential; an inductive load circuit; and a bidirectionalhighvacuum thermionic electron-discharge device having a bidirectionalelectron-discharge path coupled in series with said source and saidcircuit for controlling current flow in said circuit.

7. Signal-generating apparatus comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes spacedfrom one another along an electron-discharge path and a controlelectrode disposed across said path intermediate said cathodes; a so rceof input signals; an input circuit including a coil coupled to saidcontrol electrode and said input signals to said control electrode tocontrol electron space current flow between said cathodes; a loadcircuit coupled between said cathodes; and means for impressing aunidirectional operating potential difference between said cathodes and.in series with said load circuit.

8. Signal-generating apparatus comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes spacedfrom one another along an electron-discharge path and a controlelectrode disposed across said path intermediate said cathodes; a sourceof input signals; an input circuit including a coil coupled to saidcontrol electrode and to one of said cathodes for applying said inputsignals to said control electrode to control electron space current fiowbetween said cathodes; a current-limiting resistor included in saidinput circuit and coupled in series with said control electrode and saidone cathode; a load circuit coupled between said cathodes; and means forimpressing a unidirectional operating potential difference between saidcathodes and in series with said load circuit.

9. Signal-generating apparatus comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol electrode intermediate said cathodes; a source of input signalscoupled to said control electrode and to one of said cathodes to controlelectron space current flow between said cathodes; an inductive loadcircuit coupled between said cathodes; and means for impressing aunidirectional operating potential diiierence between said cathodes andin series with said load circuit.

10. Signal-generating apparatus comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes; a load circuit and a source ofunidirectional operating potential coupled in series between saidcathodes; and a source of negative-polarity pulses coupled between saidcontrol grid and one of said cathodes for intermittently interruptingelectron space current flow between said cathodes.

11. Signal-generating apparatus comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes; a load circuit and a source ofunidirectional operating potential coupled in series between saidcathodes; and means including an input circuit coupled to said controlgrid and to one of said cathodes and including a currentdimitingresistor and a grid-biasing condenser for applying a control signalbetween said grid and said one cathode to control electron space currentflow between said cathodes.

l2. Signal-generating apparatus comprising: a bidirectional high-Vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes; a load circuit and a source ofunidirectional operating potential coupled in series between saidcathodes; and means including an input circuit coupled to said controlgrid and to one of said cathodes and comprising means coupled to saidload circuit for applying a control signal between said grid and saidone cathode to control electron space current flow between saidcathodes.

13. Signahgenerating apparatus comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes; an inductive load circuit and asource of unidirectional operating potential coupled in series be tweensaid cathodes; and means including an input circuit coupled to saidcontrol grid and to one of said cathodes and comprising a feedback coilinductively coupled to said load circuit for applying a control signalbetween said control grid and said one cathode to control electron spacecurrent flow between said cathodes.

14. Signal-generating apparatus comprising: a bidirectional high-vacuuznelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes and having an effectiveamplification factor as measured from said grid to one of said cathodes;an inductive load circuit and a source of unidirec tional operatingpotential coupled in series between said cathodcs; and means includingan input circuit coupled to said control grid and to the other of saidcathodes and comprising a feedback coil inductively coupled to said loadcircuit and having a voltage ratio with respect to said circuitsubstantially equal to the reciprocal of said amplification factor forapplying a control signal between said grid and said other cathode tocontrol electron space current flow between said cathodes.

l5. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectrondischarge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow thercbetween; an input circuit including an inductorcoupled between said grid and one of said cathodes; an input-signalsource coupled to said input circuit for applying to said control gridinput pulses of predetermined time duration short relative to theirperiodicity; an output circuit coupled between said cathodes andresonating at a frequency having a period at least equal tosubstantially twice said predetermined time duration; and means forimpressing a unidirectional operating potential difference between saidcathodes and in series with said output circuit.

16. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectrondischarge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an input circuit including an inductorcoupled between said grid and one of said cathodes; an input-signalsource coupled to said input circuit for applying to said control gridinput pulses of predetermined time duration short relative to theirperiodicity; an output transformer having primary and secondary windingsand having an efiective capacity shunting said primary winding ofmagnitude to resonate with said primary winding at a frequency having aperiod at least equal to substantially twice said predetermined timeduration; and means for impressing a unidirectional operating potentialdifference between said cathodes and in series with said primarywinding.

17. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an output inductor and a source ofunidirectional operating potential coupled in series between saidcathodes; an input circuit including a coil coupled between said gridand one of said cathodes; an input-signa1 source coupled to said inputcircuit for applying to said control grid periodic input pulses ofpredetermined time duration short relative to their periodicity; andmeans effectively providing across said output inductor a capacity ofmagnitude to resonate with said output inductor at a frequency having aperiod at least equal to substantially twice said predetermined timeduration.

18. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an output inductor and a source ofunidirectional operating potential coupled in series between saidcathodes; an input circuit including an inductor, a current-limitingresistor, and a grid-biasing condenser coupled between said control gridand one of said cathodes; an input-signal source coupled to said inputcircuit for applying to said control grid periodic input pulses ofpredetermined time duration short relative to their periodicity; andmeans effectively providing across said output inductor a capacity ofmagnitude to resonate with said output inductor at a frequency having aperiod at least equal to substantially twice said predetermined timeduration.

19. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectron-discharge device having, a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an output inductor and a source ofunidirectional operating potential coupled in series between saidcathodes to provide a series output current path; an input circuitcoupled to said control grid and to one of said cathodes and including afeedback coil coupled to said output inductor; an input-signal sourcecoupled to said input circuit for applying to said control grid periodicinput pulses of predetermined time duration short relative to theirperiodicity; and means effectively providing across said output inductora capacity of magnitude to resonate with said output inductor at afrequency having a period at least equal to substantially twice saidpredetermined time duration.

20. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuum electron-discharge device having a pair of thermionic cathodes and a controlgrid intermediate said cathodes and having an effective amplificationfactor measured from said grid to one of said cathodes; an outputinductor and a source of unidirectional operating potential coupled inseries between said cathodes; an input circuit coupled to said controlgrid and to the other of said cathodes and including a feedback coilinductively coupled to said output inductor and having a voltage ratiowith respect to said inductor substan tially equal to the reciprocal ofsaid amplification factor; an input-signal source coupled to said inputcircuit for applying to said control grid periodic input pulses ofpredetermined time duration short relative to their periodicity; andmeans efiectively providing across said output inductor a capacity ofmagnitude to resonate with said output inductor at a frequency having aperiod at least equal to substantially twice said pre determined timeduration.

21. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectron-discharge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an output inductor and a source ofunidirectional operating potential cou pled in series between saidcathodes to provide a series output current path; an input circuitcoupled to said control grid and to one of said cathodes; means includedin said series output current path and coupled to said input circuit forapplying a control potential to said control grid; an input-signalsource coupled to said input circuit for applying to said control gridperiodic input pulses of predetermined time duration coupled in seriesbetween said short relative to their periodicity; and means effectivelyproviding across said output inductor a capacity of magnitude toresonate with said output inductor at a frequency having a period atleast equal to substantially twice said predetermined time duration.

22. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectron-discharge device having a pair or" thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow thcrebetween; an output inductor and a source ofunidirectional operating potential coupled in series between saidcathodes to provide a series output current path; an input circuitcoupled to said control grid and to one of said cathodes; meansincluding a transformer having a primary winding coupled in said seriesoutput current path and a secondary winding coupled in said inputcircuit for applying a control potential to said control grid; aninput-signal source coupled to said input circuit for applying to saidcontrol grid periodic input pulses of predetermined time duration shortrelative to their periodicity; and means effectively providing acrosssaid output inductor a capacity of mag nitude to resonate with saidoutput inductor at a frequency having a period at least equal tosubstantially twice said predetermined time duration.

23. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectrondischarge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an output inductor and a source ofunidirectional operating potential coupled in series between saidcathodes to provide a series output-current path; an input circuitcoupled to said control grid and to one of said cathodes; means includedin said series outputcurrent path and coupled to said input circuit forapplying a control potential to said control grid; a feedback coilincluded in said input Circuit and coupled to said output inductor; aninput signal source coupled to said input circuit for applying to saidcontrol grid periodic input pulses of predetermined time duration shortrelative to their periodicity; and means eifectively providing acrosssaid output inductor a capacity of magnitude to resonate with saidoutput inductor at a frequency having a period at least equal tosubstantially twice said predetermined time duration.

24. Signal-generating apparatus for generating an output current ofsawtooth waveform comprising: a bidirectional high-vacuumelectrondischarge device having a pair of thermionic cathodes and acontrol grid intermediate said cathodes for controlling electron spacecurrent flow therebetween; an output inductor and a source ofunidirectional operating potential cathodes to provide seriesoutput-current path; an input circuit coupled to said control grid andto one of said cathodes; means including a transformer having a primarywinding coupled in said series output current path and a secondarywinding series-coupled in said input circuit for applying a ccntrolpotential to said control grid; a feedact. coil included in said inputcircuit and cou to said output inductor; an input-signal source coupledto said input circuit for applying I to said :controlwgrid fperiodicinput pulses magnitude toresonate-with said output inductor at afrequency having a period at least equal to substantially twice saidpredetermined time du' ration;

25; Signal-generating -apparatus for generating an outputcurrent: ofi=sawt'ootl1' waveform comprising: a bidirectional: high-vacuumelectrondischarge device-having :a pair of thermionic cathodes and-"acontrolgrid intermediate said cathodes and-ha'v-ingan efiectiveamplification factorineasuredfromsaid grid-to one of said cathodes;anoutput'"inductor and a sourceof unidirectional'-operating: potentialcoupled in series between'said cathodes to provide a seriesoutput-current-path; an input'circuit coupled to said control gr-id andto one'of' said cathodes; ineans' including a transformer having a pri-'mar-y winding coupled in said series output-current path and aseconda'rywinding series-coupled in said in'put circuit for'applying-acontrol potential to said control-grid; a feedback coil included insaidinputucircuitand-coupled to said output inductor and 'having avoltage ratio With and-means effectively-providingacross=said output"inductor a capacity of respect to 1 said :1 outputs. inductorsubstantially' equal-1 to":=the 'recip'rocal -ofl said: amplificationfactor an rinput-signal source coupled to said input"circuitfor-applying tosaid control" grid. periodic input :pulses ofpredetefimined timecduration short relative to-the'ir periodicity; and"means :effectively providing across said output inductor a capacity ofmagnitude to resonate with saidoutput inductor at a frequency havingaperiod at least equal to substantially twice said predetermined timeduration.

References Cited in /-the file of-this patent v UNITED "STATES" PATENTSNumber Name Date 1,201,273 De'Fo'rrest Oct. 17, 1916 1,629,009 Snookl;May.17, 1927 2,037,202 Terman v; Apr. 4, 1936-- 2,218,331 Etzrodt";Oct.'15', 1940 2,228,276 LeVan.- .Jan.i14; 1941 2,242,351 Etzrodt MayZO,1941 2,288,363 McArthur June 30, 1942 2,377,456 Spitz'er June 5, '1945"FOREIGN:PATENTS Number Country Date 214,025 Switzerland July 1, 1941'-

